We propose to be a clinical center for the Clinical Trials of Hypertension Prevention. In the first Phase, I-A and B, of this clinical trial we propose to test the short and intermediate term blood pressure lowering efficacy of oral calcium, magnesium and omega-3 fatty acid supplement as single agents, in dual combination and all three in combination as compared to a placebo control group, in persons with high normal diastolic blood pressures. We plan to enroll males between the ages of 25 to 45 and females between the ages of 35 and 50 with a diastolic blood pressure of between 78 and 89mm Hg who are not being treated with drugs for hypertension. The rationale for the study is based on animal experimental, clinical and epidemiological evidence for the association of these micronutrients on blood pressure. Other current studies in our Department and research group are testing the efficacy of sodium reduction, potassium increase and weight reduction, as well as decreased alcohol intake and stress management in the reduction of blood pressure. This study would test other non-pharmacological approaches which may be effective. The design is a supplement trial which will examine the increase in a single nutrient with the diet essentially being unchanged. The appoach minimizes the type of compliance difficulties encountered in major nutrient intervention studies which require dietary modifications and allow for a focus on a central single nutrient hypothesis. The design also may be double blinded. Changes in blood pressure will be the primary outcome measure investigated. We will also be investigating characteristics of responders and non-responders to particular nutrient supplement and supplement combinations. We propose during the first phase to test these interventions, and to measure adherence and side effects. We plan to work closely with other groups and the NIH staff. We also would be willing to modify the proposal based on the decisions of the Steering Committee of the Trial including the measurements of other nutrients.